We are the reason why there are a lot of altcoins as of bow and our current era those people who accept the value of a certain coin will be decided but if they are not accepting it it is just a worthless coin they give value so people can buy it and make profits from it if the coin is not popular it is a coin with no value at all
If you are seeing the fact that most of the altcoin was generated from the ICO, remember the ico has a fixed price to the token. And the price of the altcoin detemined by divide the total amount raised with the total supply of the token. The community give the more value to the coin. It's pegged with the total raised amount. The airdrop token based on the interest by the investors.